package title;

import java.util.Scanner;

/**
 * 功能：
 * 作者：lc
 * 日期：2024/11/23 18:28
 */
public class Main1002 {
    public static void main(String[] args) {
        long[][] dp = new long[25][25];
        int[] dx = {-1, -2, -2, -1, 1, 2, 2, 1};
        int[] dy = {-2, -1, 1, 2, 2, 1, -1, -2};
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int m = scanner.nextInt();
        int x = scanner.nextInt();
        int y = scanner.nextInt();
        dp[0][0] = 1;
        for (int i = 0; i <= n; i++) {
            for (int j = 0; j <= m; j++) {
                if (i == 0 && j == 0) continue;
                boolean ok = true;
                if (i == x && j == y) ok = false;
                for (int k = 0; k < 8; k++) {
                    if (i == dx[k] + x && j == dy[k] + y) {
                        ok = false;
                        break;
                    }

                }
                if (ok) {
                    if (i - 1 < 0) {
                        dp[i][j] = dp[i][j - 1];
                    } else if (j - 1 < 0) {
                        dp[i][j] = dp[i - 1][j];
                    } else {
                        dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                    }
                }
            }

        }
        System.out.println(dp[n][m]);


    }
}
